Railway track circuit apparatus



June 14, 1938. o. GRONDAHL 2,120,837

RAILWAY TRACK CIRCUIT APPARATUS Original Filed Jan. 6, '1934 2 Sheets-Sheet 1 4 25 F )2 24\ 3, a )0 I E I], I:

g INVENTOR 45 121 g Lam 061 0120216! H [S A TTORNEY June 14, 1938 1.. o. GRONDAH L 2,120,837

RAILWAY TRACK CIRCUIT APPARATUS Original Filed Jan. 6, 1934 2 Sheets-Sheet 2 Pmazzem M0912?! myz INVENTOR Laps 0.6fr012qalzl BY MINA 4 H! S A TTORNEY Patented June 14, 1938 UNITED STATES PATENT OFFICE RAILWAY TRACK CIRCUIT APPARATUS Application January 6, 1934, Serial No. 705,558 Renewed November 24, 1934 25 Claims.

My invention relates to railway track circuit apparatus of the type involving a source of current and a relay each connected across the rails of a section of track. One feature of my invention is the provision of apparatus for improving the shunting sensitivity and the reliability of such a railway track circuit.

I will describe several forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagrammatic view showing one form of track circuit apparatus embodying my invention and suitable for use with direct current track circuits. Fig. 2 is a diagrammatic view showing a modified form of direct current track circuit apparatus embodying my invention. Figs. 3 and 4 are each a diagrammatic view showing a form of apparatus embodying my invention and suitable for use with alternating current track circuits. Figs. 5, 6 and '7 are modified forms of the apparatus illustrated in Fig. 1, and each of which embodies my invention.

In each of the several views like reference characters designate similar parts.

Referring to Fig. 1, the reference characters I and I designate the rails of a railway track which rails are divided by insulated rail joints 2 to form a track section E--F. This section is provided with a track circuit comprising as its essential elements the rails bonded in the customary manner, a source of current connected across the rails at one end of the section, and an electroresponsive means connected across the rails at the opposite end of the section. As here shown, the source of current is a battery 4 one terminal of which is connected with the rail I over wire 5 and its opposite terminal connected with the rail I through a current limiting resistor 5. It follows that the battery 4 constantly supplies direct current to the rails of the section E-F.

At the right-hand end of section E-F is located an electroresponsive means which includes two relays RI and R2. Relay RI is a differential relay and is shown conventionally as a magnetizable core I3 and an armature I6 pivotally mounted at the point I I. The armature I6 is preferably biased to a middle position, that is, to the position illustrated in Fig. 1, and is capable of swinging either toward the pole face I8 or I9 of the core I3. On the outer end of the armature I6 is mounted a contact member 29 preferably insulated from the remaining portion of the armature as indicated at 52. Contact member 20 is adapted to bridge contacts 9-4! completing the connection therethrough when the armature I6 is in its middle position, and to open the connection therethrough when the armature is drawn either toward the pole face I 8 or I9. Two windings I4 and I5 are mounted on the core I3 and are so disposed that when winding I5 alone is energized, the armature I6 is pulled toward the pole face I9, and if winding I4 alone is energized, the armature is pulled toward the pole face I8, whereas, if both windings I4 and I5 are energized, the pull on the armature is in opposite directions. Hence, if the two windings I4 and I5 are energized by currents of such value as to produce fluxes of substantially equal force, the armature I6 is retained in its middle position where the contact 9El is closed. Relay R2 is a direct current track relay and may be either of the neutral or polarized type. As here shown, relay R2 is a neutral relay having an armature II capable of being lifted into engagement with a front contact I2 in response to the energizing of the relay. The armature II may be utilized for controlling a signal governing traffic through the section E--F, or other traffic governing device in any desired manner.

Winding M of relay RI is connected across the rails I and I over the wires I and I0, a resistor 2| being interposed in the wire I. The winding of the relay R2 is also connected across the rails I and I by a circuit traced from rail I over wire I, winding of relay R2, wire 8, contact 9Il of relay RI and wire I!) to the rail I. The winding I5 of the relay RI is energized from any convenient source such as a battery 22, an adjustable resistor 23 being interposed in the connection as will be readily understood by an inspection of Fig. 1. One terminal of the winding I5 is also connected by a wire 24 with the mid point of a resistor 25 spanning the rails I and I The opposite terminal of the winding I5 is also connected with a ground electrode 21 by a wire 26. It follows that the circuit including wire 24, resistor 25, distributed rail to ballast resistance of the section E--F, ground, ground electrode 2'! and wire 26, constitutes a shunt path to the winding I5.

As is well understood in the railway signaling art, the ballast leakage resistance of a track section, that is, the resistance from rail to rail through the ties and ballast and also the resist ance from rails to ground, varies through wide limits, depending upon weather conditions. When the ballast is wet, this leakage resistance is comparatively low, but when the ballast is dry or frozen, the leakage resistance is comparatively high. That is to say, weather conditions will affect the resistance from rail to rail of the section EF, the resistance between the rails and ground and also the ground resistance, the variations of these resistances caused by changes in weather conditions being substantially alike in behavior. It is clear, therefore, that the shunt =path traced above for the winding I5 will be affected by weather conditions and will tend to make the current flow in the winding I5 vary in about the same way as the track circuit will cause the current flow in the winding I4 to vary in response to changes in weather conditions.

The parts of the apparatus of Fig. 1 are so proportioned that under normal conditions the fluxes created by the windings I4 and I5 are of substantially equal value and the armature I6 remains in the middle position closing the contact 99 With contact 9-43 closed, the track relay R2 is energized in the usual manner by current supplied from the track circuit and its armature II will be lifted into engagement with the front contact I2. Inasmuch as variations in the flow of current in the winding I4 due to variations in the ballast resistance from rail to rail caused by changes in weather conditions will be accompanied by like variations in the flow of current in winding I5 due to variations in the rail to ground resistance caused by the same changes in weather conditions, the fluxes created by these two windings will be increased and decreased in step with each other and will substantially balance, as far as their pull exerted upon the armature I6 is concerned, under all weather conditions.

When a vehicle enters the section the train shunt will very materially reduce the flow of current in the winding I4 but will affect little, if any, the flow of current in the winding I5. This unbalancing of the fluxes created by the windings I4 and I5 will be in favor of winding I5 and the armature I6 will be pulled to the left opening the cont-act 99 and in turn depriving the track relay R2 of all current. Relay R2 will, therefore, be quickly deenergized and its armature released in response to the vehicle entering the section E-F. Relay R2 will, of course, be shunted in the usual manner when the vehicle enters the section and will subsequently release its armature in response to the train shunt even though the contact 99 were to remain closed.

It is the intent to energize the windings I4 and I5 of relay RI to several times the value necessary to operate the relay armature. A relatively small reduction in the current in one winding will, therefore, produce motion of the armature so that a train shunt resistance that reduces the current of winding I4 by, say, only 10% will be sufiicient to open the contact 9-9=* in the circuit of the track relay R2, where-as a much larger percent of reduction in the track circuit current would be required to shunt the relay R2 in the usual manner. That is to say, a relatively small percent of reduction in the track circuit current will unbalance the differential relay RI and cause movement of its armature and the subsequent deenergizing of the track relay R2, whereas a relatively large percent of reduction in the track circuit current would be required to release the armature of the track relay R2 in the usual manner. In the case of light weight high speed vehicles the train shunt may not be of suiiicient low resistance to release the track relay in the customary manner. This train shunt, however, will be suificient, even though it is of relatively high resistance, to reduce the flow of current in the winding I4 of the differen tial relay RI to a point where the fluxes are unbalanced enough to cause operation of the arm-ature I6 and a subsequent deenergization of the track relay R2. It is clear, therefore, that relays RI and R2 form a relay combination which will be highly sensitive to train shunts, and whose operation will not be readily affected by the variations caused by changes in weather conditions.

In Fig. 2, the apparatus is similar to that in Fig. 1 except the winding I5 of relay RI is energized over a circuit including a portion of the rails I and I in parallel. This circuit can be traced from the battery 22 over adjustable resistor 23, midpoint of resistor 25, rails I and I in parallel, resistor 28 to its midpoint, wire 29, winding I5 of relay RI and to the opposite terminal of battery 22. The top terminal of winding I5 is connected with the ground electrode 21, and consequently, the rail to ground resistance forms a shunt path to the winding I5. The resistor 23 serves both to adjust the energization of the winding I 5 and to give the potential drop necessary to obtain the desired shunting effect of the ground path. In view of the foregoing description of the apparatus of Fig. 1, it is clear that the relay RI of Fig. 2 will retain its balance during variations in ballast resistance caused by changes in weather conditions and will be highly sensitive to a train shunt resistance with the result that operation of the track relay R2 and the subsequent operation of the traflic governing device will be assured.

In Fig. 3, the section EF is provided with an alternating current track circuit and the differential relay RI is supplied with current through the medium of rectifiers. The primary winding 30 of a transformer T is connected with any convenient source of alternating current not shown, and its secondary winding 32 is connected across the rails I and l a current-limiting reactor 3! being interposed in the connection with rail I. At the relay end of the section the input terminals of a full-wave rectifier 33 are connected across the rails I and I over wires 34 and 35, and its output terminals are connected across the winding I4 of the relay RI and hence this winding is energized with rectified current received from the track circuit. An alternating current track relay R3 of the usual type is connected with the rails of the section over the contact 99 of the relay RI as will be readily understood by an inspection of Fig, 3. The winding of relay RI is, in this instance, supplied with current from a transformer T2 through a full-wave rectifier 36, the circuit being traced from the righthand terminal of the secondary winding 3'! of transformer T2 over reactor 38, resistor 39, rails I and I in parallel, resistor 40, wire 4|, one side of rectifier 35, winding I5, the other side of rectifier 36 and wire 42 to the left-hand terminal of the secondary winding 31. The left-hand terminal of the secondary winding 3'! is connected with a ground electrode 43, and hence the rail to ground resistance forms a shunt path to the winding I5. It is clear, in view of what has already been said in connection with the apparatus of Figs. 1 and 2, that by proper proportioning of the parts, the fluxes created by windings I4 and I5 of the relay RI of Fig. 3 will substantially balance under the ordinary variations of ballast resistance caused by changes in weather conditions, and that the contact 9---9 will be normally closed, completing the circuit for the track relay R3, the armature 44 of which may be utilized to control a traflic governing device in any desired manner. Relay RI of Fig. 3 will preferably be energized to a point where a relatively small percent of reduction in the current supplied to either winding I4 or I5 will be suflicient to cause movement of the armature. Consequently, the relays RI and R3 of Fig. 3 will respond quickly to a vehicle entering the section although the train shunt may not be low enough to shunt the track relay R3 in the usual manner.

In Fig. 4, the source of power is also alternating current, but the circuit for the winding I5 of relay RI is entirely removed from the track rails and is completed through the ground electrodes 44, 45 and 46. The circuit in this instance extends from the right-hand terminal of the secondary winding 31 of transformer T2 through reactor 38, ground electrode 44, ground resistance, ground electrode 45, one side of rectifier 36, winding I5, the other side of rectifier 36 and wire 41 to the left-hand terminal of the secondary winding 31. The third ground electrode 46 is connected with the left-hand terminal of the secondary winding 31 and hence forms a shunt path to the winding I5. These ground electrodes are so positioned with respect to the section EF that the ground shunt resistance on the winding I5 will be similar in its behavior with respect to changes in weather conditions to that of the ballast leakage resistance of the track circuit to the same changes in weather conditions. Consequently, a balance for the differential relay RI will be maintained under the various weather conditions and the relays RI and R3 will respond to a train shunt in the same manner as the relays of Fig. 3. The ground connections shown in Fig. 4 have the advantage that they are entirely independent of the presence of a vehicle in the section but will require that they be carefully made in order that variations in the ground resistance caused by changes in weather conditions are substantially identical to the variations of the ballast leakage resistance of the track circuit.

In Fig. 5, the circuit for winding I5 of relay RI is removed from the track rails and is completed through the ground electrodes 44, 45 and 46 the same as in Fig. 4, the source of power, however, being in this instance the battery 24. In this form of the apparatus the usual track relay is replaced by a repeater relay R4 which is energized from a local source of current here shown as a battery 41 over the contact 9---9 of the differential relay RI. This form of apparatus has the advantage that all the power supplied from the track circuit may be used to energize the winding I4 of the relay RI.

In Fig. 6, the connection for the winding l5 of the differential relay RI is the same as Fig. 1, while the repeater relay R4 is energized over the contact 9-9 of relay RI from the battery 46 of the track section adjacent the section EF. With this arrangement all the power received from the track circuit is available for energizing the winding I4 of relay RI and an extra source of current for energizing the repeater relay R4 is avoided. In View of the foregoing description, it is clear that the operation of the differential relay RI and the repeater relay R4 of both Figs. 5 and 6 will be similar to the operation of the differential relay RI and the track relays R2 and R3 of the preceding figures. The repeater relay R4 may be employed to control traffic governing means as desired. It will be noted in connection with Fig. 6 that the repeater relay R4 is connected with the track battery 48 inside the usual current-limiting resistor 5I and shunting of the track rails of the section associated with battery 48 will not shunt the relay R4.

In Fig. '7, the differential relay RI is provided with means for latching the armature I6 in the open position once it has been operated by the track winding I4. The armature I6 may be latched either mechanically or magnetically and as here shown, the relay RI is provided with a permanent magnet shown conventionally at M whose pole face 49 is so positioned with respect to the armature I6 that in the middle position of the armature the air gap is great enough that the effect of the permanent magnet on the armature is negligible. When the armature I6 is attracted to the right due to the flux of winding I4, the force of the permanent magnet on the armature rapidly increases. The parts are so proportioned that armature I6 when swung to the right makes contact with the pole face 49 of the permanent magnet and is held in its right-hand position until it is released manually notwithstanding the biasing means provided for retaining the armature in the middle position. The current for energizing the winding I5 is carried over a contact 5IJ5I1 adapted to be closed when the armature I6 occupies its middle position and also when it is swung to the left under the influence of the winding I5, and to be opened when the armature is swung to the right under the influence of the winding I4. The parts of the apparatus of Fig. 7 are so proportioned that a balance is maintained for the differential relay RI during variations of the ballast resistance caused by changes in weather conditions. A train shunt will materially reduce the current in the winding I4 and armature I6 will be pulled to the left to open the contact 9-53 and operate the track relay R2 the same as pointed out hereinbefore. If, for any reason, the circuit for the winding I5 fails and the flow of current therethrough is reduced, the armature IE will be pulled to the right due to the normal influence of winding I4, and once swung to the right, the armature I6 will be magnetically latched in the extreme righthand position until it is manually released. It follows that failure of the apparatus due to improper energization of the winding I5 can ocour only on the side of safety. In addition to providing a latching device the permanent magnet M of Fig. 7 may be so positioned as to provide an additional bias on the armature I6 so that in case of a loss of current in both windings I4 and I5 at the same time, the armature I6 will be pulled to the right to open both contacts 99 and 50-50 Although I have herein shown and described only certain forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without depart ing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: g

1. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a winding for receiving energy from the track rails of the section, a circuit controlling armature adapted to be moved by the force developed by said winding, means for establishing a force which opposes and substantially balances the normal force of said winding on the armature, and an auxiliary circuit including a ground connection for varying the force of said means in response to variations in the ground resistance to maintain the balance of said forces during changes in weather conditions.

2. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a first winding receiving current from the rails of the section and responsive to variations in the ballast resistance of the section due to changes in weather conditions as well as to trafiic conditions of the rails, a second winding for said relay receiving current and arranged to oppose and balance the force of the first winding, a ground connection, an auxiliary circuit including said ground connection and responsive to variations in the ground resistance caused by changes in weather conditions for varying the current supplied to the second winding to maintain the balance of said forces during changes in weather conditions, and a circuit controlling armature governed by the windings of the relay.

3. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a first winding receiving current from the rails of the section and which current is responsive to variations in the ballast resistance of the section due to changes in weather conditions as well as to traffic conditions of the rails, a second winding for said relay receiving current and arranged to oppose and substantially balance out the force of the first winding, a ground connection, an auxiliary circuit including said ground connection and responsive to variations in the ground resistance caused by changes in weather conditions for varying the current supplied to the second winding by amounts which are substantially equal to the variations produced in the current supplied to said first winding in response to changes in weather conditions, and a circuit controlling armature governed by the windings of the relay.

4. In combination with a section of railway track and a source of current connected across the rails of said section, an auxiliary souuce of current, a relay having a first winding receiving energy from the rails of the section in series and a second winding receiving energy from said auxiliary source, an armature subjected to opposing forces created by the fluxes due to current in said two windings respectively, a contact operated by said armature and closed when such opposing forces are substantially balanced but open when the armature moves in response to unbalancing of such forces, a ground connection, an auxiliary circuit including said ground connection and responsive to variations in the ground resistance due to changes in weather conditions for varying the energy supplied to the second winding for balancing the variations in energy supplied to said first winding due to changes in weather conditions, and traffic governing means controlled by said contact.

5. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having two windings, means for connecting one of said windings across the rails of the section, another source of current, means for connecting the other winding and said other source of current with the rails of the section in parallel and with ground, said windings arranged that their fluxes oppose and are substantially equal, an armature subjected to the opposing forces of the fluxes of said windings,

a contact operated by said armature and closed when such forces are substantially equal but open when the armature moves in response to such forces becoming unequal, and traffic controlling means controlled by said contact.

6. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having two wind-,

ings, means for connecting one of said windings across the rails of the section, another source of current, means for connecting the other winding and said other source of current with the rails of the section in parallel, said windings arranged that their fluxes oppose and are substantially equal, an armature subjected to the opposing forces of the fluxes, a contact operated by said armature and closed when such forces are substantially equal but open when the armature moves in response to such forces becoming unequal, traffic controlled means controlled by said contact, and means for grounding said other winding whereby variations of the ballast resistance of the section cause substantially like variations in the fluxes of said windings.

'7. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a winding receiving current from the rails of the section the value of which is varied in response to variations in the ballast resistance due to change in weather conditions as well as to the shunting of the rails, an armature adapted to be moved by the force developed by said winding, means for establishing a force which opposes and substantially balances the normal force of said winding on the armature, a ground electrode, an auxiliary circuit including said electrode responsive to variations in the resistance between the rails and said electrode for varying the force of said means by amounts substantially equal to the variations in the force of said winding caused by changes in weather conditions to maintain the balance of said forces, whereby said armature is unaffected by weather conditions but is operated in'response to the shunting of the rails, and a traffic controlling means governed by said armature.

8. In combination with a section of railway track and a source of current connected across the rails of the section, a first and a second relay, a first winding for said first relay connected across the rails of the section to receive current from'said source, a second winding for said first relay receiving current and arranged that its flux opposes and substantially balances the flux of the first winding, an armature subjected to the forces of said opposing fluxes, a contact operated by said armature and closed when such forces are substantially balanced but open when the armature moves in response to unbalancing of such forces, means for energizing the second relay including said contact, and a traffic governing means controlled by the second relay.

9. In combination with a section of railway track and a source of current connected across the rails of the section, a first and a second relay, a first winding for said first relay connected across the rails of the section to receive current from said source, a second winding for said first relay receiving current and arranged that its flux opposes and substantially balances the flux of the first winding, an armature subjected to the forces of said opposing fluxes, a contact operated by said armature and closed when such forces are substantially balanced but open when the armature moves in response to unbalancing of such forces, an auxiliary circuit including a ground connection and responsive to variations in ground resistance for varying the current supplied to said second winding to maintain the balance of said fluxes during changes in weather conditions, means for energizing the second relay including said contact, and traffic governing means controlled by the second relay.

10. In combination with a section of railway track and a source of current connected across the rails of the section, a first and a second relay, a first winding for said first relay connected across the rails of the section to receive current from said source, a second winding for said first relay receiving current and arranged that its flux opposes and substantially balances the flux of the first winding, an armature subjected to the forces of said opposing fluxes, a contact operated by said armature and closed when such forces are substantially balanced but open when the armature moves in response to unbalancing of such forces, an auxiliary circuit including a ground connection and responsive to variations in ground resistance for varying the current supplied to said second winding to maintain the balance of said fluxes during changes in Weather conditions, means for connecting the second relay across the rails of the section and including said contact, and traffic governing means controlled by the second relay.

11. In combination with a section of railway track and a source of current connected across the rails of the section, a first relay having a first winding connected across the rails of the section to receive current from said source and a second winding receiving current and arranged that its flux opposes and substantially balances the flux of the first winding, an armature subjected to the forces of said opposing fluxes, a contact operated by said armature and closed when such forces are substantially balanced but open when the armature moves in response to unbalancing of such forces by either winding, 9, trafiic controlling relay controlled by said con tact, an auxiliary circuit including a. ground connection and responsive to variations in ground resistance for varying the current supplied to said second winding to maintain the balance of said fluxes during changes in weather conditions, and another contact operated by said armature and Y open only when the armature is moved by the first winding for controlling the current to the second winding.

12. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a first winding connected across the rails of the section to receive current from said source and a second winding receiving current and arranged that its flux opposes and substantially balances the flux of the first winding, an armature subjected to the forces of said opposing fluxes and occupying a middle position when such fluxes balance but which is moved to the right or left when the fluxes of the first or second windings respectively predominate, an auxiliary circuit including a ground connection and responsive to variations in ground resistance for varying the current supplied to said second winding to maintain the balance of said fluxes during changes in weather conditions, a first contact operated by said armature and closed when the armature occupies the middle position but open when the armature is moved to the right by the first winding for controlling the current to said second winding, a

traflic controlling contact operated by said armature and closed only when the armature occupies the middle position, and means for latching the armature when moved by the first winding.

13. In combination with a section of railway track and a source of current connected across the rails of the section, a differential relay, means connecting one Winding of said relay across the rails for receiving current from said source, circuit means for supplying current to the other winding of the relay including the rails in parallel and a ground connection, said windings arranged that the forces or" their respective fluxes normally balance whereby variations in ballast resistance caused by changes in weather conditions are ineifective to unbalance such forces but such forces are unbalanced in response to the shunting oi the rails of the section, and traffic governing means for the section controlled by said relay.

14. In combination with a section of railway track and a source of current connected across the rails of the section, a differential relay, means for connecting one Winding of said relay across the rails for receiving current from said source, circuit means for supplying current to the other winding of the relay including a ground connection and arranged that its flux substantially balances the flux of said one winding, a contact operated by the armature of said relay and closed when the fluxes are substantially balanced but open when the armature moves in response to unbalancing of such fluxes, a second relay, means for energizing the second relay including said contact, and a trafiic governing means controlled by the second relay.

15. In combination with a section of railway track and a source of current connected across the rails of the section, a circuit controlling device, means for supplying energy for operating said device to a circuit controlling condition, other means for supplying energy from the track rails to said device for substantially neutralizing the efiect of the operating energy for maintain=- ing the device in an inoperative condition, and means including a ground path for varying said operating energy in response to variations in ground resistance whereby the effect of said operating energy remains substantially neutralized by the track energy irrespective of changes in weather conditions.

16. In combination with a section of railway track and a source of current connected across the rails of the section, a circuit controlling device, means for supplying energy for operating said device to a circuit controlling condition, other means for supplying energy from the track rails to said device for opposing the effect of the operating energy to maintain the device in an inoperative condition so long as said section remains unoccupied and to cause. said device to assume its circuit controlling condition when said section becomes occupied, and means including a ground path for automatically varying said operating energy in response to variations in ground resistance in such manner as to maintain said device in its inoperative condition irrespective of changes in weather conditions as long as said section remains unoccupied.

17. In combination with a section of railway track and a source of current connected across the rails of the section, a normally inoperative relay having a first and a second winding, means for energizing said first winding from the rails of said section, means for energizing said second winding in such manner as to oppose the effect of the flux set up by said first winding, a circuit including a ground path for producing variations in the energization of said second winding in response to changes in weather conditions which are substantially proportional to the variations in the energization of said first winding caused by said changes in weather conditions whereby said relay will normally remain inoperative but will become operative in response to a change in the energization of said first winding resulting from the entry of a train into said section, and traflic controlling means governed by said relay.

18. In combination with a section of railway track and a source of current connected across the rails of the section, a normally inoperative difierential relay, means for supplying operating energy to said relay, means including the track rails for supplying energy from said source to said relay in such manner as to oppose said operating energy to maintain said relay normally inoperative but to render said relay operative in response to the entry of a train into said section, and a ground path for by-passing a portion of said operating energy away from said relay in accordance with changes in weather conditions.

19. In combination with a section of railway track and a source of current connected across the rails of the section, a difierential relay, means for supplying operating energy to said relay, means including the track rails for supplying energy from said source to said relay in such manner as to oppose said operating energy to render said relay inoperative when said section is unoccupied and to render said relay operative due to the decrease in said opposing energy resulting from said section becoming occupied, and a shunt path including the ground for bypassing a portion of said operating energy away from said relay to vary said operating energy in accordance with changes in weather conditions whereby said relay will be maintained inoperative when said changes occur unless said section becomes occupied.

20. In combination; a section of railway track; a track circuit for said section including a track relay; an auxiliary relay actuated in response to a change in current flow in said circuit, said auxiliary relay characterized by being substantially more quickly responsive than said track relay to the entrance of a train into said section; and means controlled by said auxiliary relay for supplementing the effect of the entrance of said train on said track relay.

21. In combination, a section of railway track, a source of track circuit current and a track relay for said section, an auxiliary relay energized from said source over a track-connected circuit and responsive to the change in track current occurring when a train enters said section but incapable of responding to changes in said current resulting from changes in ballast resistance, said auxiliary relay remaining effective during the occupancy of said section by said train, and means including a contact of said auxiliary relay for supplementing the effect of the entry of said train on said track relay.

22. In combination, a section of railway track, a source of track circuit current and a track relayfor said section, an auxiliary relay energized from said source over a track-connected circuit and responsive to the change in track current occurring when a train enters said section but incapable of responding to changes in said current resulting from changes in ballast resistance, said auxiliary relay remaining effective during the occupancy of said section by said train, and means including a contact of said auxiliary relay for decreasing the energization of said track relay.

23. In combination, a section of railway track, a track circuit for said section including a source of current and a track relay, an auxiliary relay responsive to the change in current flow in said circuit occurring when atrain enters said section but incapable of responding to changes in current flow resulting from changes in ballast resistance of said section, said auxiliary relay remaining effective during the occupancy of said section by said train, and means controlled by said auxiliary relay for supplementing the effect of the entrance of said train on said tracl; relay.

24. In combination, a section of railway track, a track circuit for said section including a source of current and a track relay, an auxiliary relay controlled by current flowing in said track circuit and responsive to the change in said current occurring when a train enters said section but incapable of responding to changes in said current resulting from changes in ballast resistance of said section, said auxiliary relay remaining eiiective during the occupancy of said section by said train, and means controlled by said auxiliary relay for aiding the release of said track relay.

25. In combination, a section of railway track, a track circuit for said section including a source of ciurent and a track relay, an electro-responsive device controlled by current flowing in said track circuit and responsive to the change in said current occurring when a train enters said section but incapable of responding to changes in said current resulting from changes in ballast resistance of said section, said electro-responsive device remaining effective during the occupancy of said section by said train, and means governed by said electro-responsive device for controlling the energization of said track relay.

LARS OL GRONDAHL. 

